1. Field of the Invention
The present invention relates to providing means to hold and to electrically ground the metal bracket portions of conventional expansion card assemblies in place within a computing system, and, more particularly, to using a single latching bar for this purpose, so that the individual screws conventionally used are not required.
2. Background Information
A conventional computing system includes a number of positions, often called "slots," in which one or more expansion cards may be installed. These cards allow the flexible configuration of the system hardware, providing I/O functions, communication functions, etc. Signal and voltage lines are brought to each expansion card from a system bus through a number of bus connectors. The use of expansion cards in this way has become so widespread that several architectures, or electrical and mechanical configurations, have evolved. Of these, the most widespread have come to be called ISA (Industry Standard Architecture) and PCI (Peripheral Component Interconnect). This concept allows expansion cards from hundreds of manufacturers to be interchangeably used with computing systems from dozens of manufacturers.
In general, the expansion cards are individually plugged into a structure including a number of bus connectors aligned along a mother board, in alignment with a slotted card cage. There is one slot for each card position, together with a single connector, or with two or more connectors in axial alignment with one another on the mother board. Each expansion card includes a steel card bracket which fits inside the card cage, extending across a single slot. If the card has connectors for cables external to the system, these connectors are fastened to extend outward through an aperture in the card bracket, and hence through a slot in the card cage when the expansion card is installed in the system. Each card bracket includes an end portion turned outward to lie adjacent an inward extending portion of the card cage. Each card bracket is fastened into place using a single screw engaging this inward extending portion of the card cage through a slot within this outward turned end portion of the card bracket. This screw serves both to hold the expansion card in place, properly engaging the associated bus connector(s) and to electrically ground one end of the card as required for the maintenance of operation without excessive radio frequency emissions which may otherwise interfere with communication signals. This grounding location is often particularly important because of a need to ground cable shielding. At positions in the card cage in which an expansion card is not installed, filler panels having shapes similar to the card brackets are similarly installed to cover the slots internally. These filler panels also need to be electrically grounded to minimize radio frequency emissions.
While this configuration has gained wide acceptance, the use of a single, separate screw to hold each card bracket and each filler panel in place presents a number of problems. Since the use of expansion cards is intended to provide for easy reconfiguration of the computer system and for the expansion of its capabilities, such cards are often added or replaced by the system user. A typical problem occurring is the loss of the screw as a filler panel or expansion card is installed or removed. When a screw falls into the adjacent area, which is typically crowded with cards, cables, connectors, and other components, it is generally very difficult to find and retrieve. It must be retrieved in order to prevent a potentially damaging short circuit condition. In floor-standing computers, expansion cards are often replaced or added without disconnecting the various cables extending from the system, and therefore without moving the system off the floor. Such conditions make the removal and replacement of screws, and the retrieval of a screw in the event of a mishap, particularly difficult.
Many types of equipment, including computing equipment in other areas, have been configured to eliminate a need for using tools in areas where customer access is desirable. While the customer is expected to be able to install expansion cards, as evidenced by the fact that such cards are sold in boxes by computer stores, he must use a screwdriver to remove and reinstall the screws.
In the process of manufacturing a computer system, each slot in the card cage must be filled with either the bracket of an expansion card or with a filler panel. This means that a number of screws must be driven, increasing the time required for the assembly process.
Thus, what is needed is a method for holding expansion cards and filler panels in place in a card cage without requiring the use of a single screw for each card bracket and filler panel. Such a method should also provide for reliable electrical grounding between the card cage and the card bracket or filler panel. Furthermore, it is particularly desirable to facilitate the replacement of such cards and panels without requiring the use of a tool.